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Fractional Blackbody Emissive Power Solver. By: David Wheeler & William Tryon November 30, 2011. Introduction. It is often necessary to know the fraction of the total emission from a blackbody that is in a certain wavelength interval or band.
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Fractional Blackbody Emissive Power Solver By: David Wheeler & William Tryon November 30, 2011
Introduction • It is often necessary to know the fraction of the total emission from a blackbody that is in a certain wavelength interval or band. • A ‘Blackbody Radiation Function’ table can be used to lookup such values to calculate the total emissive power. • The calculations to find the total emissive power are long, quite monotonous, and can introduce errors. • Our object is to make this process quicker, easier, and more accurate.
Main Objectives • User Friendly • Accurate • Intuitive (no need for instructions) • Easy of Use • Universal (able to use on a wide variety of problems) • Visually Appealing • Quick • Able to accept small changes easily, in order to gain a better understanding of the material
Calculator Layout The fraction of the radiation between the specified wavelengths Define the temperature of the diffuse surface Define up to three wavelengths of interest If desired, enter the spectral, normal emissivity for the specified range Press Run! at any time to update the calculations Total emissivity Total emissive power Press Reset to erase all entries
Sample Problem • A diffuse surface at 1600K has the following spectral, hemispherical emissivity: ε = 0.40 for 0 < λ < 2μm ε = 0.80 for 2 < λ < 5μm ε = 0 for λ > 5μm Determine the total hemispherical emissivity and the total emissive power.
Sample Problem (cont.) • Enter the following parameters: • Surface temperature • λ1 and λ2 • ε1 and ε2 • Push Run! • Viola! There’s the answers!
How it Works! • We wrote a MATLAB script that interpolates the data from Table 12.1 • We then designed and programed a Graphical User Interface (GUI) to collect the required inputs • Using the interpolated data and the collected inputs, we performed the necessary calculations • We display the fractional radiation distribution, the total emissivity, and total emissive power.
Conclusion • The program is: • User Friendly • Accurate • Intuitive (no need for instructions) • Easy of Use • Universal (able to use on a wide variety of problems) • Visually Appealing • Quick • Able to accept small changes easily, in order to gain a better understanding of the material
Future Work • Ability to increase the number of specified wavelengths. • Higher order approximation for the fraction of the blackbody emission in a spectral band (currently we use a linear fit) • Create a Java applet to improve availability • Include additional outputs, such as the spectral intensity for the specified wavelength.